The present invention relates to an air flow meter, and more particularly to a heating resistor type air flow meter used for engine control in a vehicle.
In this kind of the inlet air flow measuring apparatus for a vehicle, so far, for example, as described in Japanese Patent Application Laid-Open No. 2-276914 (1990), a control unit to control the current flowing through a heating resistor element is mounted on the same substrate mounting a computer for internal combustion engine control to measure air flow rate.
In recent years, a highly accurate combustion control for a vehicle engine is required for natural environmental protection and the conservation of natural resources. Thereby, the amount of computing and controlling imposed on a computer for engine control is increasing.
The objects of the present invention can be attained by providing a heating resistor type air flow meter having a processing unit which outputs a signal corresponding to the air flow rate with use of a heating resistor mounted to an inlet pipe, which comprises an inlet mounted to the inlet pipe, with the substrate being cooled or controllable in temperature.
The objects of the present invention can be further attained by providing a heating resistor type air flow meter having a processing unit which outputs a signal corresponding to the air flow rate with use of a heating resistor mounted to inlet pipe and a cover to seal the processing unit wherein the cover is sealed with glass.
The objects of the present invention can also be attained by providing a heating resistor type air flow meter having a processing unit which outputs a signal corresponding to the air flow rate with use of a heating resistor mounted to an inlet pipe, wherein the processing unit covered with lead.
Since the air flow meter itself has a processing unit to control the temperature of a heating resistor based on a program the air flow rate can be computed independent from an engine control.
Further, since the processing unit for the air flow rate is mounted to a substrate capable of regulating temperature, a highly accurate air flow rate can be detectable even when the processing unit is installed at a high temperature position in an engine room.